This application addresses a highly significant and prevalent public health concern of young adulthood- alcohol, tobacco, nonmedical prescription drug use, and illicit drug use and related problems, which can have major consequences for personal health and safety. The focus of this application is on a potentially new risk factor for problematic ATOD use, namely, energy drinks. Energy drinks and shots are highly caffeinated beverages that are popular among adolescents and young adults. They differ from traditional caffeinated products in that they deliver higher caffeine doses and are marketed specifically to youth using messages that are related to risky behaviors. The medical community has already cautioned against energy drinks' short-term health effects, such as cardiac problems and caffeine toxicity, yet longer-term effects are poorly understood. It is plausible that energy drink consumption might contribute over time to the intensification of substance use patterns, based on prior evidence that a) energy drink consumers have above-average rates of heavy drinking and drug use, and b) high caffeine doses might enhance the addictive properties of other substances via neurobiological mechanisms. Therefore, the proposed research focuses on elucidating the longer-term interrelationships between energy drinks, alcohol, tobacco, and other drug use patterns. The investigators will analyze eight annual waves of data from a large existing longitudinal dataset (n=1,253), assembled as part of the PI's NIDA-funded study of young-adult substance use behaviors. It would be the first study to leverage longitudinal data to describe the different long-term patterns of energy drink consumption among young adults (e.g., sustained heavy use, declining use, sporadic use). This study will also identify the characteristics that distinguish between individuals with different consumption patterns, and document which of those patterns might be associated with patterns of escalating or heavy substance use over time. This application uses advanced statistical methodology (e.g., growth mixture modeling), which the research team has already used to understand longitudinal substance use patterns. This research will complement ongoing NIH-funded research focusing on the relationship between energy drink consumption and alcohol-related problems by broadening the focus to include other drugs, particularly stimulant drugs (nicotine, cocaine, prescription stimulants), which are especially likely to be influenced by caffeine's neurobiologica effects. We anticipate that findings will lay the foundation for future research with younger adolescent samples, where the risk for incident drug is high and, according to national data, energy drinks are still growing in popularity. Moreover, this research has a translational focus that can lead to policy recommendations addressing health and safety issues around energy drinks. Knowledge gained in this study will inform innovative prevention strategies for young adult substance use problems-and in that regard, be useful for students, parents, health professionals, and policy makers.